The present invention relates to an optical fiber splice sleeve and a method for applying the splice sleeve to jointed optical fibers. More specifically, the present invention relates to an optical fiber splice sleeve with a self-contained heat generating unit used for attaching the splice sleeve to the jointed optical fibers.
Optical fiber lengths are connected or jointed together for many purposes including establishing long distance links. This type of connection is called a splice. For maximum performance, the splice should have the best possible alignment between the fiber cores, and retain that alignment. Splices can generally be categorized as mechanical splices or fusion splices, based on their principle of operation. Fusion splicing is an efficient technique for permanently jointing two fibers, and is known for its ability to achieve the tight tolerances. However, very low signal loss and high mechanical strength are very difficult to achieve simultaneously in a fusion splice. Accordingly, it is necessary to protect to protect fusion spliced fibers against environmental damage and to restore adequate strength by applying a suitable reinforcement at the splice after the fusion. Several methods have been used for splice reinforcement, however, these prior splice reinforcements, and prior techniques for applying splice reinforcements have certain disadvantages associated therewith.
In a fusion splice, the two fiber ends to be jointed are prepared by removing the primary coating and are cleaved. The fiber ends are placed into engagement with one another with accurate alignment and suitable pressure, and are heated to the fusion point to weld the fibers. The splice is then reinforced by a selected method.
One conventional reinforcement method is based on the use of a splice sleeve of the kind depicted in FIG. 1. This splice sleeve 2 consists of an inner thermosetting tube 4, a steel rod 6, and an outer shrinkable tube 8. The steel rod 6 increases the strength of the splice. Before jointing, one of the two fibers, e.g., fiber 10, is inserted into the inner thermosetting tube 4. Fibers 10 and 12 are then fused, as described above, and the splice sleeve 2 is moved back over the splicing point. This section of the joined fibers are placed into a heat oven causing the inner thermosetting tube 4 to melt around the splice, and the external tube 8 to shrink around the splice pressing the steel rod 6 into the melted inner tube 4 and the jointed fibers.
However, this splice sleeve and the technique for applying this splice sleeve have some disadvantages. First, while steel rod 6 may be suitable to provide adequate strength, it may be too stiff for some applications which require that the splice sleeve have the ability for some bending. Additionally, steel rods 6 frequently have sharp edges and ends which can potentially cut or otherwise damage the jointed fibers. The steel rod 6 also inherently has a high thermal conductivity coefficient, which causes the sleeve 2 to retain heat for a significant period of time after splicing. Further, because the rod 6 is made of steel, it is also susceptible to rust and other corrosive problems.
Additionally, as many splices are performed in a field environment, the ovens used to apply heat to the sleeves are almost exclusively powered from a portable generator. This can be a problem because the heat ovens require a significant quantity of electricity to apply the splice sleeve in excess of the quantity of electricity required to affect the splice. Accordingly, applications of these splice sleeves 2 increase the possibility of wearing the portable generator down.
Therefore, an optical fiber splice sleeve was thus needed which would eliminate or reduce the deleterious effects of sharp ends and edges, and the heat retention, rigidity, and corrosive properties associated with metal rods used in prior art splice sleeves. Additionally, an optical fiber splice sleeve was thus needed which would eliminate the requirement to provide electricity to prior splice sleeves. The present invention was developed to accomplish these and other objectives.
In view of the foregoing, it is a principal object of the present invention to provide an improved optical fiber splice sleeve.
It is also an object of the invention to provide an improved optical fiber splice sleeve which eliminates the disadvantages associated with steel reinforcing rods.
Additionally, it is another object of the invention to provide an improved optical fiber splice sleeve which eliminates the necessity to supply an oven with electricity to prolong generator life and reduce the possibility of the generator running out of electricity.
These and other objects are achieved by the present invention which, according to one aspect, provides a splice sleeve for reinforcing fused first and second optical fibers at a splice. The splice sleeve includes a heat shrinkable tube, and first and second substances located within the heat shrinkable tube. The exposure of the first and second substances to each other causes a chemical reaction that produces heat.
In yet another aspect, the invention provides a splice sleeve for reinforcing fused first and second optical fibers at a splice. The splice sleeve includes a heat shrinkable tube, and a sealed chamber containing an aqueous solution located inside the tube.
In another aspect, the invention provides a splice sleeve for reinforcing fused first and second optical fibers at a splice. The splice sleeve includes an inner heat meltable tube, an outer heat shrinkable tube, and an elongated strengthening rod disposed between the inner tube and the outer tube. A chemically-activatable heat source is coupled to at least one of the tubes and is capable of generating sufficient heat, when activated, to melt the inner tube and shrink the outer tube.
The invention also provides a splice sleeve for reinforcing fused first and second optical fibers at a splice. The splice sleeve includes a heat shrinkable tube, and a chemical selected from the group of Be, Li, Na, Mg, K, Ca, Rb, Sr, Cs, Ba, Fr, and Ra, and mixtures thereof, contained inside of said heat shrinkable tube.
In yet another aspect, the invention provides a method for reinforcing fused first and second optical fibers at a point of fusion. The method includes providing a splice sleeve having a heat shrinkable tube, and positioning the splice sleeve over the point of fusion. The first and second substances are exposed to each other inside of the heat shrinkable tube. The exposure of the first and second substances to each other produces a chemical reaction giving off heat sufficient to affix the splice sleeve to the fused first and second fibers.
These and other objects and features of the invention will be apparent upon consideration of the following detailed description of preferred embodiments thereof, presented in connection with the following drawings in which like reference numerals identify like elements throughout.